Thickness Of Strata Research Articles

Effect of Drainage Failure of Diversion Channel on Anti-Floating Characteristics of Inning Structure

Many water diversion channels in China were built on thick and high-permeability super stratum, and groundwater level exerts significant influence on the anti-floating stability of the channel lining structure. The check valve drainage is an effective engineering measure for ensuring the anti-floating stability. However, people have rarely paid attention to the anti-floating calculation of lining structure once the check valve fails. This study, based on the typical cross-section of a diversion channel, investigated the characteristics of anti-floating stability of the diversion channel by using finite-element numerical simulation and theoretical analysis. The results show that reasonable calculation of anti-floating water level in the channel should be based on both numerical simulation and theoretical formula. As the check valve works normally with local failure, increasing the water level of the channel can prevent the lining structure from floating up. However, if the channel section cannot meet the anti-floating requirements when the check valve completely fails, corresponding measures should be taken in actual engineering projects to avoid the floating.

Overturned Eocene – Lower Pliocene alluvial stratum on the southern coast of Lake Baikal and its neotectonic significance

The study is focused on a section of sediments exposed on the right bank of Mishikha River, Russia. These sediments have a wide range of ages, from the Eocene to the Lower Pliocene. The stratigraphic subdivision of the section is based on the lithogeochemical data and X-ray phase analysis of the mineral compositions. The particle-size analysis shows the alluvial origin of the deposits. Their ages are constrained by spore-pollen spectra in three palynozones: I – Eocene – Oligocene, II – Early – Middle Miocene (subzone a – Tsuga, Picea in the lower part, and Quercus, Taxodiaceae, Momipites, Carya in the upper part; subzone b – Fagus, Quercus, Tsuga), and III – the Late Miocene – beginning of the Pliocene (subzone ν – Ulmus, Juglans, Carya; subzone g – Carya, Alnus). The section shows a combination of normal and overturned sedimentary layers. The tectonic displacement of the block with its flip was accompanied by the entry into contact of the unlithified Pliocene sediments with a rigid bed and the development of a landslide. The lower age limit of deformations is constrained from the youngest (beginning of the Pliocene) spore and pollen spectrum extracted from deformed layers. It is suggested that the overturned layers result from strike-slip deformations of the sediments at the beginning of the late orogenic stage of the Baikal rift development. The regional correlations of the sedimentary strata give grounds to conclude that the Mishikha section is characteristic of alluvial sedimentation that dominated at the eastern end of the Tankhoi tectonic step (Mishikha-Klyuevka paleovalley), in contrast to the Tankhoi block in the central part of the step, wherein a thick Lower Miocene stratum of swampy-oxbow sediments accumulated. The stratons of the Mishikha section correlate with sedimentary units detected by drilling in the Selenga delta at the central part of the South Baikal basin.

Design of remnant pillar in mechanized depillaring using continuous miner

Ribs and snooks are the critical natural support at the goaf edge in the mechanized depillaring operation of the bord and pillar mining system. The pillar extraction has been carried out by taking the slices and leaving ribs and snooks during the depillaring operation. Remnants are the remaining portion of the extracted pillar. The depillaring operation leads to an unsupported roof, and the immediate unsupported roof imposes its weight on the pillar (remnant) under extraction. The remnant’s purpose is to provide a necessary reaction to the overhang to restrict roof failure until the pillar’s final slice. The remnant’s stability during depillaring operation has been accessed in the study using three-dimensional numerical simulations. A scheme has also been proposed in the study to evaluate the factor of safety (FOS*) of the remnant pillar in the residual phase at different stages of slicing operation. A case of an Indian coal mine using the fish-bone method has been chosen for the study. A typical depillaring stage has been selected for the extraction of the pillar using the fish-bone method. The numerical simulation of the considered panel provides the vertical stress and yielding profile on the pillars at different stages of depillaring. The simulation results show the influence zone up to one pillar from the goaf edge. The immediate intact pillar shows considerable yielding of about 60% of the pillar area. The remnants have completely yielded during the slicing operation but provide a reaction to the immediate strata. The remnant should provide the reaction to the immediate roof till taking the final slice from the pillar. The remnant’s FOS* is calculated by taking the ratio of reaction offered by the remnant (numerical simulations) and the weight of the overhang (estimation). The area’s borehole section shows two layers of medium to coarse-grained sandstone as an immediate stratum. The weight of the immediate strata has been estimated in the study considering the immediate strata’s thickness. Two different scenarios of immediate strata thickness (i.e., 4.75 m and 9 m) have been considered in the study to evaluate the remnant’s FOS at different depillaring stages.

Whether the Middle Eocene Salt-Forming Brine in the Kuqa Basin Reached the Potash-Forming Stage: Quantitative Evidence from Halite Fluid Inclusions

The Kuqa Basin is an important potentially potash-bearing basin in China, and thick salt-bearing strata were deposited under the influence of multistage Tethyan transgression-regression cycles during the Eocene. At present, research on the process of potash formation in the Kuqa Basin has mostly focused on traditional salt mineralogy, whole-rock geochemistry, and evaporite sedimentary evolution characteristics. However, research on the original ore-forming parent fluid directly related to potash formation has not yet been carried out, directly hindering further evaluation of potash mineralization. Therefore, this paper takes the internal factors controlling potash formation as the starting point and analyzes the physical and chemical properties, such as the homogenization temperatures ( T h ) and chemical compositions, of primary halite fluid inclusions. A total of 220 T h data from fluid inclusions were obtained, and the temperatures ranged from 9.4 to 54.1°C, indicating a high-temperature brine environment conducive to the rapid deposition of the potash deposit. In total, 22 halite fluid inclusions were analyzed for chemical components. The highest KCl content reached 0.59%, which was higher than the lowest industrial grade of potassium-rich brine (0.5%), indicating that the brine experienced a high degree of evaporation and concentration during the salt-forming period and reached the potash precipitation stage. This paper provides quantitative data on the evolution of the sedimentary environment in the Kuqa Basin and supports future potash exploration.

Mechanism and Prevention and Control of Mine Earthquake in Thick and Hard Rock Strata considering the Horizontal Stress Evolution of Stope

This study investigated the mechanism, prevention measures, and control methods for earthquake disasters typically occurring in mines with thick and hard rock strata. A mine stope with large faults and thick hard rock strata in Hebei Province was taken as the background study object. Then, theoretical analysis and numerical simulation methods were adopted in conjunction with field monitoring to explore how horizontal stress evolves in the thick and hard hanging roofs of such mines, potentially leading to mining earthquakes. Then, based on the obtained results, a mining design method was proposed to reduce the horizontal stress levels of earthquake mitigation. The results showed that, under the control of large faults, semiopen and semiclosed stopes with thick hard rock strata are formed, which cause influentially pressurized and depressurized zones during the evolution of the overburden movements and horizontal stress. It was determined that the stress concentrations mainly originated from the release and transfer of horizontal stress during the rock fractures and movements in the roof areas, which were calculated using a theoretical estimation model. The horizontal stress concentrations formed “counter torques” at both ends of the thick and hard strata, which prevented the support ending due to tensile failures. As a result, the limit spans were increased. This study proposed a mining strategy of using narrow working faces, strip mining processes, and reasonable mining speeds, which could effectively reduce horizontal stress concentrations and consequently prevent and control mining earthquakes. This study’s research results were successfully applied to the mining practices in working face 16103.

Differences in the Tectonic Evolution of Basins in the Central‐Southern South China Sea and their Hydrocarbon Accumulation Conditions

AbstractTo reveal the causes of differences in the hydrocarbon accumulation in continental marginal basins in the central‐southern South China Sea, we used gravity‐magnetic, seismic, drilling, and outcrop data to investigate the tectonic histories of the basins and explore how these tectonic events controlled the hydrocarbon accumulation conditions in these basins. During the subduction of the Cenozoic proto‐South China Sea and the expansion of the new South China Sea, the continental margin basins in the central‐southern South China Sea could be classified as one of three types of epicontinental basins: southern extensional‐foreland basins, western extensional‐strike slip basins, and central extensional‐drift basins. Because these basins have different tectonic and sedimentary histories, they also differ in their accumulated hydrocarbon resources. During the Cenozoic, the basin groups in the southern South China Sea generally progressed through three stages: faulting and subsidence from the late Eocene to the early Miocene, inversion and uplift in the middle Miocene, and subsidence since the late Miocene. Hydrocarbon source rocks with marine–continental transitional facies dominated by II–III kerogen largely developed in extremely thick Miocene sedimentary series with the filling characteristics being mainly deep‐water deposits in the early stage and shallow water deposits in the late stage. With well‐developed sandstone and carbonate reservoirs, this stratum has a strong hydrocarbon generation potential. During the Cenozoic, the basin groups in the western South China Sea also progressed through the three developmental stages discussed previously. Hydrocarbon source rocks with lacustrine facies, marine‐continental transitional facies, and terrigenous marine facies dominated by II2–III kerogen largely developed in the relatively thick stratum with the filling characteristics being mainly lacustrine deposits in the early stage and marine deposits in the late stage. As a reservoir comprised of self‐generated and self‐stored sandstone, this unit also has a high hydrocarbon generation potential. Throughout those same three developmental stages, the basin groups in the central South China Sea generated hydrocarbon source rocks with terrigenous marine facies dominated by III kerogen that have developed in a stratum with medium thicknesses with the filling characteristics being mainly sandstone in the early stage and carbonate in the late stage. This reservoir, which is dominated by lower‐generation and upper‐storage carbonate rocks, also has a high hydrocarbon generation potential.

Research on seismic exploration techniques and methods in urban environment of loess plateau

Seismic wave energy being absorbed strongly in thick loose loess stratum is a major problem that seismic exploration has to face. In the urban environment, this problem is particularly prominent due to the inability to use explosives, borehole explosion, and large-scale 3D observation methods to increase fold number. To solve this difficult problem, a series of seismic exploration effect tests were carried out in Shaoling Plateau, a southern suburb of Xi’an City. A large-tonnage vibroseis, 28-ton vibrator vehicle, was selected as seismic source. By comparing and analyzing the effects of various vibrating parameter of vibrator vehicle, cooperating with different model geophones acquisition, and using appropriate observation system, we had figured out the feasible parameters for the source excitation and data acquisition in the field working area. Based on the results of above test, a nearly 7 km long seismic survey line was completed with pretty good data acquisition, and the expected exploration aims were well achieved.

Study on Surrounding Rock Movement of Fully Mechanized Top-Coal Caving with Strong Impact Under Thick-Hard Strata

In view of the serious damage of roadway and the severe roof weighting of the 3302 working face, microseismic monitoring and surrounding rock displacement monitoring system were used to conduct on-line in-situ monitoring. In this paper, the energy distribution and microseismic event distribution of stope in the primary impact stage and the “square” stage (The working face is pushed to the stage where the strike length of the mined-out area is equal to the dip length, i.e., the stage of “square” of the working face.) are studied. On this basis, the deformation and failure law of the roadways is analyzed. Furthermore, the breaking regularity of multiple thick and hard strata with fully mechanized top-coal caving is obtained. Due to the high span of the fully mechanized caving face, the failure region of the overlying strata expands. As the fracture of the 3rd hard layer, the rotation and deformation of the upper rocks expand. With the periodic fracture of the 3rd hard layer, the hanging area of the 6th hard rock layer increases, which finally leads to its fracture. The weighting of stope is severe during the “square” stage, which is recorded through field monitoring. Through the preliminary analysis, it is concluded that the fracture of the 3rd and the 6th hard stratum contribute to the severe weighting during the “squire” stage, which is easy to induce rock burst. Over the primary impact period, the occurrence of seismic events is frequent and the ground pressure is strong. The maximum approach between two sides of roadway is about 750 mm, and that between the top and bottom is 1300 mm. The periodic weighting of three different “source points” is analyzed by numerical simulation. It is found that the peak value of leading abutment pressure in “square” stage is 82.09 MPa. Finally, the high risk zone of rock burst is obtained, and the predictable “pressure relief zone” is determined, which provides an important reference value for the prevention of rock burst in multi-layer thick and hard rock strata in a super kilometer deep well.

Археологические комплексы эпохи голоцена из Денисовой пещеры: материалы 2021 года

This article provides new research data resulting from an analysis of Holocene deposits excavated at the far end of south chamber in Denisova Cave. 1.6 m thick strata were examined in an area of 12 square meters. Lithological Layers 0, 2, and the upper part of Layer 3, have mostly yielded the pottery fragments dated to the Early Iron Age. The vessels were decorated with rows of pits, “pearls”, impressions produced by the corner section of a spatula, and with an affixed smooth or dissected band. A stemmed bone arrowhead with an octagonal cross-section has been associated with this complex as well. The pottery vessel fragments from the lower part of Layer 3 ornamented with impressions of the vertically positioned comb stamp were attributed to the Middle Bronze Age. Pottery found in the same part of the stratigraphic section and Layers 4 and 5 shows features typical of the Afanasievo culture dating back to the Early Bronze Age. The pottery dishware was decorated with a zigzag pattern, imprints from a cord and obliquely arranged sticks, inclined impressions of a smooth or combed stamp, and horizontal grooves. The lithic inventory associated with the Afanasievo complex includes a carefully treated bifacial stemmed arrowhead, crescent-shaped knife, scrapers of various types, retouched flakes, and large pebble tools. Scarcely represented lithic tools, including the fragments of insets from Layer 8, may be attributed to the early Holocene. In general, the 2021 excavations showed that, during the Bronze and Iron Ages, humans inhabited the dark and narrow areas of the cave far from its entrance just as actively as the relatively bright and spacious parts of the site.

Использование многолетнемерзлых пород для закачки дренажных вод коренных месторождений алмазов на примере участка «Ноябрьский» (рудник «Айхал»)

Thick permafrost strata in the territory of the Yakutsk diamondiferous province make it possible to take into account and use this natural favorable factor in environmental protection. For the environmentally safe exploitation of the fields, ALROSA is injecting drainage water into the existing and developed in the permafrost strata reservoirs. Consequently, an important research problem is assessment of the resulting impact of injection on the state of the geological environment by designing a method for predicting the position of the technogenic horizon for the estimated life of the field. The parameters of the planned distribution of the injected drainage water were obtained by the geophysical methods and study of the regime of the piezometric surface. The capacity of the drainage brine injection site was estimated based on the injection results in the mode of pilot operations. The conducted studies and calculations allow us concluding that the use of the method of drainage water pumping into permafrost from the Aykhal mine on the Noyabrskiy site made it possible to reduce the impact of mining operations on the geological environment and surroundings, eliminating the possibility of brines to contaminate the surface water. Key words: permafrost

Assessment of the tectonic role of the Triassic evaporites in the North Toulon fold-thrust belt

The eastern Beausset Syncline and Toulon Belt, in the southern France, represents the easternmost remnant of the Pyrenean Apto-Albian Rift System and of the Pyrenean-Provençal orogen (Late Cretaceous-Eocene). Detailed structural and stratigraphic field mapping as well as the integration of published structural and stratigraphic data, are used to reconstruct the Jurassic to Late Cretaceous tectonic evolution of this area. A layered evaporite sequence, composed of a succession of evaporitic units interbedded with more competent lithologies, behaved as the main decoupling horizon and source of diapiric bodies. Structural and lithostratigraphic observations in the Mont Caumes area are interpreted as halokinetic in origin (wedges, flaps, welds, thrust welds, highly localized depocentes). These were controlled by the sinuous Mont Caumes salt wall that grew along the southern flank of the eastern Beausset Syncline and interacted with regional tectonic stresses from Early Jurassic to latest Santonian times. Jurassic and Lower Cretaceous carbonate units thin toward the Mont Caumes salt wall, recording deposition in salt controlled broad synclinal depocentres controlled by early salt mobilization. Inverted relics of Apto-Albian rift depocenters are aligned along the northern margin of the Toulon Belt and the adjacent Bandol Belt to the west. In the Turonian-Coniacian Revest depocenter, stratal thickness variations, progressive unconformities lateral depocentre, and the westward increase in stratal, overturning of a flap on the basin’s southern margin all record localized strong asymmetrical growth of the 3D Mont Caumes salt wall. During Pyrenean-Provençal N-S convergence starting in Early Campanian, the salt wall was squeezed and reactivated as a thrust weld. The upper part of the flap was sheared and thrust north over the Beausset Syncline (Mont Caumes imbricate). Further to the west, the Saint-Cyr salt extrusion associated with the Santonian-Muschelkalk unconformity, indicates that the Bandol salt wall extruded at the same time as the main diapiric activity of the Mont Caumes salt wall. Compressional reactivation further extruded the salt body leading to emplacement of the Beausset Klippe onto the Beausset Syncline. The Toulon salt structures can be correlated with other examples of contractional salt structures in the external Alps and Pyrenees.

New technology for mineral deposits prediction to identify prospective areas in the Zhezkazgan ore region

Purpose. Exploration and predicting the prospective areas in the Zhezkazgan ore region to set up detailed prospecting and evaluation works using new integrated technologies of prediction constructions in the mineral deposits geology. Methods. An integrated methodological approach is used, including methods for deciphering the Earth’s remote sensing (ERS) data, the use of geophysical data and methods of analogy and actualism. All constructions are made in accordance with the principles of shock-explosive tectonics (SET). Prediction constructions are started with the selection of remote sensing data for the studied region and interpretation based on the processing of radar satellite images obtained from the Radarsat-1 satellite. The radar satellite images are processed in the Erdas Imagine software package. Findings. New local prospective areas have been identified, within which it is expected to discover the deposits. Their reserves are to replenish the depleted ore base in the Zhezkazgan region. Area of the gravity maximum 1 (the Near), considered to be the most promising, is located in close proximity to the city of Zhezkazgan; area of the gravity maximum 2 (the Middle); area of the gravity maximum 3 (the Distant-Tabylga); area of the gravity maximum 6 (the Central). A prospective area has been also revealed, overlaid by a loose sediment cover and located inside the Terekty ring structure, as well as the area of a thick stratum of pyritized grey sandstones, which is adjacent to the Sh-2 well drilled to the south of the Zhezkazgan field. Originality. The use of a new prediction technology, in contrast to the known ones, is conditioned by the widespread use of the latest remote information from satellite images, which increases the accuracy of identifying the prospective areas of fields. Practical implications. The new technology for predicting mineral deposits makes it possible to significantly reduce the areas exposed to priority prospecting, which provides significant cost savings.

Ground heave movement evaluation in shallow foundations for expansive soils in Tunja, Colombia

A current challenge in unsaturated soil mechanics is the need to estimate ground heave and associated shallow foundation movements in expansive soils due to water content changes. Such estimation should be simple for geotechnical engineering practitioners and provide reliable foundation designs through quantifying the risk associated with the ground heave. The difficulties in generalizing a method are related to several variables influencing the expansive behavior, including the initial and final stress state condition, soil mineralogical composition, ground wetting depth, soil wetting degree, and geotechnical profile comprising soil strata thickness and groundwater condition. In this research, the evaluation of heave movements for the expansive soils located in the north-east of Tunja (Colombia) is performed through surrogate path (SPM), water content, and consolidation theory-based methods. Initial and final suction profiles were defined to quantify the wetting strains developed at each scenario of partial wetting. The sensitivity of the SPM to the estimated or measured value of constant volume swelling pressure was corroborated. The higher deformations that the soil profile would be able to develop when subjected to a progressive wetting were obtained along with the remaining heave capacity of the soil profile. Finally, concluding remarks and recommendations associated with the practicality and applicability of the methods are presented.

Study on the clay weakening characteristics in deep unconsolidated layer using the multi-point monitoring system of FBG sensor arrays

A large area of thick unconsolidated stratum layer overlying the coal seam of eastern China, which brought the regional disaster prevention issue under the circumstance of unconsolidated layer settlement triggered by mining activities. In this paper, the multi-point monitoring system based on fiber Bragg grating (FBG) sensors array was implemented into the deep unconsolidated layer to realize a long-term ground monitoring, which investigated the compression process of ground rock layers at different burial depths and revealed the mechanical weakening characteristics of clay. The deformation characteristics of the aquifers were analyzed, including a sand layer, gravel layer, and clay water barrier, as well as the weakening characteristics of the clay layer aquifer. The monitoring results of the FBG sensing system show that unconsolidated layer settlement usually occurs in thick and stable aquifers and adjacent clay layers, and the peripheral part of the deep clay layer in contact with the aquifer will become a weakened zone. The clay layer at such locations should also be a key monitoring layer with increasing depth. The survival rate of FBG sensors were discussed to propose the suggestions of system installation. These findings could provide important guidance for predicting the unconsolidated layer settlement process and for the timely implementation of governance measures.

Stratigraphic framework and sediment wave fields associated with canyon-levee systems in the Huatung Basin offshore Taiwan Orogen

Newly compiled bathymetry, sub-bottom profiling and seismic data are used to illustrate seafloor morphology, submarine canyon networks and stratigraphic framework in Huatung Basin (HB) and an adjacent sub-basin, named as East Luzon Arc Basin offshore east Taiwan. Based on seismic facies characteristics and isopach maps, three major stratigraphic sequences are recognized and we suggest that they could be resulted from pre- and syn-Taiwan arc-continent collision. Based on the sediment thickness and sedimentation rates, ages of the HB strata could be estimated. Pelagic sediments formed the lower HB sequence which follows the HB basement reliefs since 50–102 Ma. Then, the initiation of Taiwan orogen and Luzon Arc volcanic activities changed the deposition pattern after 5 Ma, and mass transport deposits developed in middle HB sequence. After rapid uplift of the Taiwan mountain belt since about 1.5 Ma, complex canyon-levee systems and thick strata formed the upper sequence in the northern HB. In contrast, sediment thickness is thin and no submarine canyon developed in southern HB. The seafloor in South Huatung Basin is flat, except in its eastern part where couple basement ridges appeared. In North Huatung Basin, canyon-levee complex and sediment waves are the most distinct morphological features in the drainages of two submarine canyons. We propose a three-stage process for sediment wave development: (1) sediment gravity flow can initiate a base of sediment wave; (2) wavy geometry begins to develop; (3) sediment waves continuously aggrade due to overbank sediments in the canyon-levee system. This study presents the evolution of sedimentary processes in a deep-sea basin and how the deposition patterns were affected by the convergent tectonics.

Breaking and Instability Movement Characteristics of High-Position Double-Layer Hard Thick Strata due to Longwall Mining

With multilayer hard roof occurring above the mining area, the strata behaviors will be significantly affected by their special characteristics and interaction. In this paper, relying on the mining background of panel 1061 of a coalmine, the breaking instability of double-layer hard thick strata (DLHTS) and the precursory information of disasters are studied by using theoretical analysis, numerical simulation, and physical simulation. Results show that the DLHTS have bearing, blocking, and controlling effects. Prior to DLHTS breaking, the horizontal development of stress concentration zone and plastic zone can be controlled, and the overburden movement is gentle, while during the breaking process, the stress drops abruptly, the plastic zone expands longitudinally rapidly, the overburden moves notably, and the energy release is sharp, which is likely to directly cause strong dynamic pressure. Moreover, the DLHTS can interact with and influence each other; that is to say, the breaking of lower magmatic rock (LMR) can provide sufficient space for that of upper magmatic rock (UMR), while the UMR breaking can promote the LMR periodic breaking in turn and cause its secondary instability, thereby easily causing complex or composite dynamic disasters’ formation. Hence, compared with single hard thick stratum occurrence, the strata behaviors affected by DLHTS breaking and instability are normal and more intense. Study results can provide a scientific basis for the prevention and control of dynamic disaster with hard thick stratum occurrence and important guidance value for promoting safe and efficient production of coalmines.

TRANSMISSION COEFFICIENT OF POWER DENSITY INTO SKIN TISSUE BETWEEN 6 AND 300 GHZ.

The latest electromagnetic safety guidelines define transmitted or epithelial power density as the basic restriction above 6GHz. In this note, we derive an approximation for a conservative transmission coefficient for quasi plane wave incidence as a function of the frequency for the normal component of the Poynting vector with respect to the evaluation plane or tissue surface |Sz inc| and for its modulus ||Sinc||. The maximum transmission coefficient for the normal component of the Poynting vector ${\boldsymbol{T}}_{\mathbf{z}}^{\mathbf{max}}$ is 1 independent of tissue composition and frequency. Approximations of ${\boldsymbol{T}}_{\mathbf{total}}^{\mathbf{max}}$ normalized to ||Sinc|| for thin and thick stratum corneum are provided allowing higher exposures. These approximations allow to conservatively demonstrate compliance with basic restrictions when quasi plane-wave conditions are locally satisfied and enhancement effects of standing waves between source and body can be neglected. The reported results are important to regulators and standardization bodies regarding revisions of compliance requirements and safety guidelines.

Analysis of the influence of stratum on karst development features: Taking Longtan river basin in Youyang County as an example

As the carrier of karst water, the stratum is capable of impacting the water yield property and karst development features, so this paper aims to find out how the stratum characteristics affect the karst water. The study site was Longtan river basin, a typical area of karst topography, located in Youyang County, Chongqing, China. Throng the statistics and analysis of the characteristics of karst water and strata, it was obvious that the thickness of strata has a significant impact on the karst water. In epi-karst, it was demonstrated that as the rock layer thickened, the flow of karst water decreased, but the number of karst springs tended to increase. The influence law was similar in deep layers, that is the relation between the stratum thickness and the average flow could be fitted by a power function, and the stratum thickness and the length of underground river, an exponential one. In addition, the flow-rate of water yielded was likely to drop fairly rapidly while the strata get deeper. Therefore, this paper successfully put forward a method, which can estimate the water resources quantity of karst water as long as the stratum thickness was available and provide a reference for the subsequent evaluation of water-abundance.

The Pliocene deposits of the Black Sea Shelf east of the Danube River Delta

Abstract This paper provides analysis of the published materials on the occurrences of the Dacian and Cimmerian molluscs in the Danube River valley as well as the results of Pliocene sediments study based on core material of the boreholes drilled at the Black Sea Shelf east of the Danube River Delta. In the early Pontian time, the Dacian Basin was a large sub-basin of Paratethys which, due to an abrupt drop in sea level, separated into the Euxinian, Dacian and Caspian basins. At the end of the Bosphorus time, the discharge of the Dacian Basin waters into the Euxinian Basin formed a wide valley from the Galati-Reni region to the east through the Galati gateway. During the Cimmerian transgression, a vast bay existed on the site of the modern Danube Delta, from which mutual migrations of the Dacian and Cimmerian molluscs took place along the runoff valley. The cessation of runoff occurred during the regressive phase of the Late Cimmerian. The rhythmically bedded thick strata originated during the existence of the runoff valley. These strata were identified as the Pridanubian Formation (Suite). The cryptogenic form of Tulotoma Tulotoma ( =Viviparus ) ovidii nasonis (Bogachev) is characteristic of the lower and middle parts of the suite. The presence of the Dacian and Cimmerian molluscs in this suite became the basis for the correlation of sediments of the Dacian and Cimmerian regional stages. The Duabian molluscs were registered in the Cimmerian deposits of the Transcaucasus (the Duabian layers), Priazovye and the Kerch–Taman region. The migration of these molluscs took place during the regressive phases due to the circular current in the Euxinian Basin similar to the one existing in the Black Sea today. The Pliocene formation contains marine and continental deposits of the Lower and Upper Pliocene, which are represented by the Pridanubian Formation (Lower and Upper), Cimmerian deposits (non-subdivided Lower and Middle Cimmerian), Lower Kujalnician deposits, Upper Poration deposits, complex of red-coloured palaeosols (the Upper Miocene–Lower Pliocene non-subdivided). The formation of the Pliocene sediments on the Black Sea Shelf, east of the Danube Delta, was controlled by the inter-basin connectivity of the Eastern Paratethys.

Geodynamic and geological factors in the formation of large hydrocarbon deposits in subsalt sediments of the North Caspian region

Background. The Astrakhan-Primorsk region of oil and gas deposits located in the North Caspian region is one of the world’s largest reserves of hydrocarbons. This region stretches from land in the northwestern part of the Caspian basin, through the northern waters of the Caspian, to the south-eastern land part of the region under consideration.Aim. To identify geodynamic and geological factors in the formation of large hydrocarbon deposits in subsalt sediments in the complex structure of the North Caspian region of the Caspian syneclise. Materials and methods. An analysis of data on the geodynamic and geological evolution of the North Caspian region of the Caspian syneclise revealed specific features of its geological structure and development.Results. The nature of the formation series, as well as the geodynamic and geological conditions (the presens of spreading and subduction zones that caused an intense heat flow, the presense of an isolated sedimentation basin with intensive accumulation of carbonates in the Upper Devonian-lower Permian, a powerful salt-bearing Kungurian cap) were favourable for the generation, migration and accumulation of hydrocarbons in large tectonic-sedimentary Upper Devonian–Lower Permian uplifts characteristic of the Astrakhan-Primorsk oil-and-gas bearing region of the North Caspian. These uplifts were formed by shelf bioherms, barrier reefs and large reeftogenic atolls and emerged through ancient troughs. The large hydrocarbon accumulations, such as Kashagan, Tengiz, Astrakhanskoye and Korolevskoye, with high specific hydrocarbon reserves (more than 100 thousand/km2) are associated with these troughs.Conclusion. During the Upper Paleozoic, the main paleodepressions of the isolated basin of the North Caspian underwent a steady and long-term subsidence process, favourable for the accumulation of a thick stratum of carbonate (mainly reef) formations. This period was also characterized by the geothermal and baric conditions necessary for the transformation and subsequent migration of hydrocarbons from oil- and gas-producing complexes to reservoirs, which were mainly presented by massive carbonate formations of reef genesis. The as-formed deposits were preserved by thick salt-bearing Kungurian sediments. Directions for prospecting and exploration works aimed at discovering new hydrocarbon deposits in the subsalt sediments of the region were outlined.